Radiographic apparatus

Abstract

An estimation selecting unit is provided to select an estimating method based on a predetermined value. When variations due to a statistical error of each pixel concerned are enlarged by a greater extent than variations of other pixels, and hence a possibility of becoming conspicuous on the image, then the direct ray transmittance at the pixel concerned is considered less than the predetermined value, and estimated direct ray intensity is obtained for the pixel concerned by interpolating calculation of estimated direct ray intensities at pixels surrounding the pixel concerned. Therefore, even when variations due to a statistical error of the pixel concerned are enlarged by a greater extent than variations of other pixels, and hence a possibility of becoming conspicuous on the image, estimated direct ray intensity is obtained for the pixel concerned by interpolating calculation of estimated direct ray intensities at pixels surrounding the pixel concerned, whereby the error can be inhibited without the pixel value of the pixel concerned being conspicuous relative to the surrounding pixels on the image.

What is claimed is: 
     
       1. A radiographic apparatus for obtaining a radiological image, comprising:
 a radiation emitting device for emitting radiation; 
 a scattered radiation removing device for removing scattered radiation, the scattered radiation removing device having absorbing layers arranged at predetermined intervals for absorbing the scattered radiation; 
 a radiation detecting device having a plurality of detecting elements arranged in rows and columns for detecting the radiation; and 
 an estimation selecting device for estimating direct radiation intensity at pixels where direct radiation is attenuated by the absorbing layers, by assuming that the absorbing layers were absent; 
 wherein the estimation selecting device is arranged, when direct radiation transmittance which is a ratio between direct radiation intensity before transmission and direct radiation intensity after transmission through the scattered radiation removing device is equal or higher than a predetermined value at each pixel concerned, to estimate direct radiation intensity for the pixel concerned using actual measurement radiation intensity at the pixel concerned obtained from actual measurement and the direct radiation transmittance, and when the direct radiation transmittance is less than the predetermined value at the pixel concerned, to estimate direct radiation intensity for the pixel concerned by interpolating calculation of direct radiation intensities at pixels surrounding the pixel concerned. 
 
     
     
       2. A radiographic apparatus for obtaining a radiological image, comprising:
 a radiation emitting device for emitting radiation; 
 a scattered radiation removing device for removing scattered radiation, the scattered radiation removing device having absorbing layers arranged at predetermined intervals for absorbing the scattered radiation; 
 a radiation detecting device having a plurality of detecting elements arranged in rows and columns for detecting the radiation; and 
 an estimation selecting device for estimating, direct radiation intensity at pixels where direct radiation is attenuated by the absorbing layers, by assuming that the absorbing layers were absent; 
 wherein, regarding direct radiation transmittance which is a ratio between direct radiation intensity before transmission and direct radiation intensity after transmission through the scattered radiation removing device, the estimation selecting device is arranged, 
 when a rate of change of the direct radiation transmittance which is a rate of change of the direct radiation transmittance in a direction along the absorbing layers is less than as predetermined value at each pixel concerned, to estimate direct radiation intensity for the pixel, concerned using actual measurement radiation intensities at the pixel concerned obtained from actual measurement and the direct radiation transmittance, and when the rate of change is equal or higher than the predetermined value at the pixel concerned, to estimate direct radiation intensity for the pixel concerned by interpolating calculation of direct radiation intensities at pixels surrounding the pixel concerned. 
 
     
     
       3. The radiographic apparatus according to  claim 1 , wherein the surrounding pixels are pixels adjoining the pixel concerned. 
     
     
       4. The radiographic apparatus according to  claim 2 , wherein the surrounding pixels are pixels adjoining the pixel concerned. 
     
     
       5. The radiographic apparatus according to  claim 1 , further comprising:
 a pixel specifying device for specifying predetermined pixels; 
 an intensity estimating device for estimating at least either of scattered radiation intensities at the predetermined pixels specified by the pixel specifying, device and direct radiation intensities at the predetermined pixels; and 
 an intensity interpolating device for interpolating at least either of scattered radiation intensities and direct radiation intensities at unspecified pixels, based on at least either of the scattered radiation intensities and the direct radiation intensities estimated by the intensity estimating device; 
 wherein the estimation selecting device is arranged, when the direct radiation transmittances are equal or higher than the predetermined value, to estimate the direct radiation intensities also using the scattered radiation intensities estimated by the intensity estimating device. 
 
     
     
       6. The radiographic apparatus according to  claim 2 , further comprising:
 a pixel specifying device for specifying predetermined pixels; 
 an intensity estimating device for estimating at least either of scattered radiation intensities at the predetermined pixels specified by the pixel specifying, device and direct radiation intensities at the predetermined pixels; and 
 an intensity interpolating device for interpolating at least either of scattered radiation intensities and direct radiation intensities at unspecified pixels, based on at least either of the scattered radiation intensities and the direct radiation intensities estimated by the intensity estimating device; 
 wherein the estimation selecting device is arranged, when the rates of change of the direct radiation transmittances are less than the predetermined value, to estimate the direct radiation intensities also using the scattered radiation intensities estimated by the intensity estimating device. 
 
     
     
       7. The radiographic apparatus according to  claim 5 , wherein, when the intensity estimating device estimates unknown radiation intensities at the predetermined pixels specified by the pixel specifying device, the pixel specifying device is arranged to determine the number of predetermined pixels to be specified according to a known number of the direct radiation transmittances which are known and a known number of the actual measurement radiation intensities which are known, and the intensity estimating device is arranged to estimate the radiation intensities by solving simultaneous equations about the actual measurement radiation intensities, the direct radiation transmittances and the radiation intensities to be estimated for the respective predetermined pixels determined. 
     
     
       8. The radiographic apparatus according to  claim 6 , wherein, when the intensity estimating, device estimates unknown radiation intensities at the predetermined pixels specified by the pixel specifying device, the pixel specifying device is arranged to determine the number of predetermined pixels to be specified according to a known number of the direct radiation transmittances which are known and a known number of the actual measurement radiation intensities which are known, and the intensity estimating device is arranged to estimate the radiation intensities by solving simultaneous equations about the actual measurement radiation intensities, the direct radiation transmittances and the radiation intensities to be estimated for the respective predetermined pixels determined. 
     
     
       9. The radiographic apparatus according to  claim 1 , wherein, when the direct radiation transmittance is less than the predetermined value, the direct radiation intensity is interpolated by linear approximation. 
     
     
       10. The radiographic apparatus according to  claim 2 , wherein, when the rate of change of the direct radiation transmittance is equal or higher than the predetermined value, the direct radiation intensity is interpolated by linear approximation. 
     
     
       11. The radiographic apparatus according to  claim 1 , wherein, when the direct radiation transmittance is less than the predetermined value, the direct radiation intensity is estimated by spline interpolation. 
     
     
       12. The radiographic apparatus according to  claim 2 , wherein, when the rate of change of the direct radiation transmittance is equal or higher than the predetermined value, the direct radiation intensity is estimated by spline interpolation. 
     
     
       13. The radiographic apparatus according to  claim 1 , wherein, when the direct radiation transmittance is less than the predetermined value, the direct radiation intensity is estimated by Lagrange interpolation. 
     
     
       14. The radiographic apparatus according to  claim 2 , wherein, when the rate of change of the direct radiation transmittance is equal or higher than the predetermined value, the direct radiation intensity is estimated by Lagrange interpolation.